This invention relates to synthetic aperture radar (SAR), and more particularly to a method and apparatus for determining the elevation of terrain features in SAR image data, and if desired for determining more accurately the distance of each pixel from the ground track of the SAR platform.
The development of SAR has made it possible to quickly map vast areas for geological as well as for defense purposes. Since topographic maps are much more useful, it would be important to use SAR for contour mapping. However, in mapping rough terrain, there is a problem in that terrain features of high altitude tend to be foreshortened (i.e., appear to be closer to the ground track of the SAR platform than they actually are), and the greater the slope of the terrain feature, the more pronounced the foreshortening effect. This is due to the fact that the range of each image pixel from the flight path is essentially determined by the slant range of the SAR platform to the reflecting points on the terrain.
It would be desirable to determine the altitude of each point on the slope, and to determine the true horizontal distance of each point from the ground flight path, in order to present an image that accurately portrays the contours in rough terrain without foreshortening.